1. Field of the Invention
The present invention relates to an ignition system for internal combustion engines wherein the ignition timing of an internal combustion engine is electronically computed, and more particularly the invention relates to an ignition system wherein the ignition timing of an internal combustion engine is controlled by feeding back the pressure in the engine cylinders to compensate the ignition timing in such a manner that the cylinder pressure attains its maximum value at the desired angular position of the engine crankshaft.
2. Description of the Prior Art
The ignition timing of an internal combustion engine must be varied in accordance with the operating conditions of the engine in a manner such that an optimum operation of the engine is ensured. The prior art ignition timing control systems generally determines the ignition timing of an engine by detecting the engine speed by a centrifugal advance mechanism and by detecting the intake vacuum pressure by a vacuum advance mechanism to represent the operating conditions of the engine by them.
It is generally known in the art that for best efficiency and fuel consumption of an engine the engine should be ignited with the so-called minimum advance for best torque (MBT), and the ignition timing of the engine must be varied in accordance with the engine operating conditions to ignite the engine at the MBT.
A disadvantage of the prior art systems of the above-type is that since an ignition timing has been programmed on the basis of the test results of an internal combustion engine, there are many instances where the ignition timing considerably deviates from the actual MBT and the programmed ignition position differs from the actual ignition point due to the atmospheric conditions, the variations in characteristics among engines of the same type, and so on, thus making it practically difficult to compensate the ignition timing and thereby failing to ignite the engine with the required spark advance, and moreover due to the fact that the compensation factors include various surrounding conditions such as the engine speed, intake vacuum pressure and temperature, the inclusion of these compensation items makes the system expensive and complicate thus making it less practical due to its construction.